1. Field of the Invention
The present invention relates to a wireless IC device, and more particularly, to a wireless IC device which is preferably used in a non-contact RFID (Radio Frequency Identification) system, and a method for manufacturing the same.
2. Description of the Related Art
In recent years, wireless IC devices including a wireless IC chip which can electronically store information for article management and process a predetermined wireless signal, and an antenna which performs transmission and reception of the wireless signal between the wireless IC chip and a reader/writer have been attracting attention because of their various capabilities. A system using such a wireless IC device is generally called an RFID system, and can be used for individual authentication and transmission and reception of data in various occasions in accordance with a combination of a wireless IC device (in the form of card, tag, inlet, etc.) and a reader/writer which reads from and writes to the wireless IC device.
Meanwhile, in such a non-contact RFID system, if an article to be attached to the wireless IC device contains metal, water, salt or the like, an eddy current is generated in the article, and therefore the antenna might not operate properly due to the eddy current. That is, when the antenna is attached to the article in a planar manner, an electromagnetic wave is absorbed due to the eddy current in a wireless IC device though depending on the frequency, especially one which operates in a high-frequency band, whereby the transmission and reception of information may fail or may be disabled.
Therefore, for wireless IC devices which operate in an HF band, a method in which a magnetic member is disposed between the antenna and the article has been proposed (for example, see Japanese Unexamined Patent Application Publication No. 2004-304370, Japanese Unexamined Patent Application Publication No. 2005-340759 and Japanese Unexamined Patent Application Publication No. 2006-13976). For wireless IC devices which operate in a UHF band, a method in which the antenna is disposed so as to be apart from the article has been proposed (see Japanese Unexamined Patent Application Publication No. 2007-172369 and Japanese Unexamined Patent Application Publication No. 2007-172527).
However, it is required that wireless IC devices be small and thin for various applications. When a magnetic member is disposed between the antenna and the article or when the antenna is disposed so as to be apart from the article, reduction in size and thickness cannot be fully achieved.